It’s not very often that a Nobel Prize-winning economist who is known for his bearish calls turns extremely bullish.

Last week, professor Robert Shiller of Yale, who called the housing collapse 10 years ago, proclaimed that stocks could rise another 50 percent in the next few years based upon his latest research. Meaning Dow 30,000!

That got the attention of many folks, especially the Wall Street analysts, many of whom don’t understand this market.

Shiller accurately saw the housing bubble and predicted that it would end very badly, as it did. He also co-developed the S&P/Case-Shiller index, which is a benchmark to measuring housing prices around major US cities.

What many may not know is that in the 1990s he developed a stock price measurement ratio called the cyclically adjusted price-to-earnings (CAPE) ratio for stock valuations.

The CAPE ratio measures stock prices in relation to long-term earnings and inflation. At current levels, Shiller’s own CAPE ratio is not flashing a buying opportunity, which makes his call even more interesting.

In fact, based on his CAPE ratio, stock prices are actually high right now. However, like many of the other ratios out there in academia and on Wall Street, interest rates are not weighted in it.

In fact, Shiller pointed out that the CAPE ratio he trusts is actually expensive now at 29. Its average is 17.

“I would say, have some stocks in your portfolio. It could go up 50 percent from here. That’s what it did around 2000 — after it reached this level, it went up another 50 percent.”

In 2000 the economy was about 12 months away from the top of the internet bubble, which also ended badly.

The key to Shiller’s call is President Trump’s tax policy. “If factors go right and there are tax cuts for corporations, it’s not that hard to understand.”

So making a great short call followed up a decade later by a great long call would give Shiller an A+ in my book. And make investors a pretty penny along the way.